Flexible liquid-packaging is used to package many consumer goods, particularly food and beverages, which are often packaged in pouches made from flexible materials. The term “liquid-packaging” is understood by those of skill in the art to refer to both liquids and other flowable materials or product.
Two aspects are important in flexible liquid-packaging: (i) optimal headspace in the pouch; and (ii) optimal fill-accuracy of the flowable material contained in each pouch. By “optimal” or “optimized” is meant that the two important factors—headspace over the product in the pouch, and fill-accuracy of the product amount in the pouch—are minimized without sacrificing one over the other such that both factors remain acceptable for packaging use. It should be noted that minimizing one factor tends to adversely affect the other factor. Ideally the goal is fill-accuracy of 100% of target weight and a headspace of 0 cm3. Practically, however, there is a trade off between good fill-accuracy and the amount of headspace in the pouch. Typically an improvement in fill-accuracy will result in a larger headspace volume. Similarly, lower headspace generally results in poor fill-accuracy. Therefore, optimizing and controlling these two parameters is the challenge for vertical form-fill-seal technology.
During pouch formation, oxygen is commonly trapped in the headspace above the product. However, many pouch products are particularly sensitive to oxygen degradation. Specifically in the food industry, many products require minimal oxygen exposure to protect their flavor, color, nutritive value, texture, and/or shelf-life. Oxygen reacts readily with some of these product components forming “off-flavors” and “off-colors”. If oxygen is removed during the packaging process, then, for example, shelf-life of the food can be extended without loss of flavor. Thus, minimizing oxygen, and in turn, minimizing headspace in a pouch, is a desired objective in pouch formation.
Besides minimizing oxygen exposure, minimal headspace facilitates pouch insertion into a secondary container—a common packaging arrangement in which the flexible pouch is inserted in a cardboard box (“bag-in-box”). A slack pouch is easier to insert into a box and will better form to shape than an inflated pouch (that is, one with a large, air-filled headspace).
Fill-accuracy, that is reducing over-fill and under-fill of the pouch, is important because it can have economic or government regulatory implications. For example, many jurisdictions require that the advertised product quantity must be the minimum product quantity. Stated another way, the laws of the jurisdiction require that the amount of product in the pouch may be more than what is advertised, but not less. Thus, if the fill-accuracy is poor, a vendor, to comply with the law, must fill the pouch with product amount more than what is advertised. Therefore, poor fill-accuracy raises business cost for the vendor. Consequently, both limiting headspace and fill-accuracy should be adequately controlled. One known method for minimizing headspace involves filling the tube for making a pouch above the level of the pouch and sealing through the product. However, this method can suffer from poor fill-accuracy and product interfering with seal formation.
Thus, achieving good fill-accuracy and/or minimal headspace would help minimize product waste, minimize oxygen in the formed pouch, and allow for the final product to fit more easily into smaller packaging.
Several methods have been used to minimize fill-accuracy and headspace. The best fill-accuracy can be achieved by limiting interaction on the pouch in a way that relies only on the delivery system and non-critical pouch making devices. However, this results in unacceptably large headspace for production runs. On the other hand, minimal headspace can be achieved by having the product completely fill the current pouch and overfill into the next upstream pouch, so when the final seal is made, there is little or no air in the first pouch. Typical devices either press above or below the product zone after the pouch has indexed. Devices that press on the pouch above the product zone results in a minor reduction of headspace while maintaining good fill-accuracy. Devices that press on the pouch around the product zone can effectively raise the product above the sealing apparatus minimizing and/or eliminating headspace, but sacrificing fill-accuracy. It is important to note that cautious control of any device must be exercised while film is indexing to avoid film hang-up which would result in machine shutdown.
It is an object of the present invention to limit the above-mentioned disadvantages. Specifically, the present invention provides a process, apparatus, and a pouch in which the headspace has been minimized with a simultaneous increase in the accuracy of filling of the flowable material into the pouch. In addition, the present invention will also provide for higher pouch production rates. The asynchronous deflation process (one of the embodiments of the invention described infra) will allow the user to accommodate variations in film runnability, allowing for variety in film conditions without being limited by the speed of the machine.